Increase In Operating Pressure Research Articles

DROPLET SIZE AND DRIFT POTENTIAL FROM MICRO-SPRAYER IRRIGATION EMITTERS

ABSTRACT A laser probe instrument was utilized to determine droplet size distributions from micro-sprayer emitters. Tests were conducted on several types of devices with nozzle sizes ranging in diameter from 0.8 mm to 1.5 mm over the range of pressures normally used on farms (150-250 kPa). Two micro-spinners were further tested in an open field to determine their behavior in windy conditions (wind speed 1.5-4.6 m/s). Measured volume mean droplet diameters for all tests ranged between 0.25 mm and 0.71 mm. Differences in droplet size distributions were found with changes in pressure, nozzle size, and impact plate geometry. Increasing operating pressure for a fixed nozzle size produced smaller droplets. Generally, increasing nozzle diameter resulted in smaller size droplets for constant pressure. Micro-sprayers with coarse impact plates produced relatively uniform droplet sizes. High wind speed and high operating pressure lowered the micro-sprayer's distribution characteristic.

Reduction of fuel-NO by increased operating pressure in a laboratory-scale coal gasifier

Measurements of NO during laboratory-scale gasification of a Utah bituminous coal verified that small increases in pressure (from 1 to 2 atm) at constant residence time resulted in dramatic decreases in effluent NO levels. Tests were conducted at 3 target levels of pressure (1, 2 and 4 atm) and 2 target levels of residence time (450 and 900 ms). Oxygen-to-coal ratio for all tests was 0.90 (stoichiometric ratio SR = 0.45). The dominant factor in causing lower effluent NO levels was the increased kinetic rate of NO decay. Increased residence time in the fuel-rich gasifier contributed to lower effluent NO levels, but was of minor importance when compared to the effect of pressure on the decay rate. Concentrations of N 2 appeared to be slightly increased and concentrations of total fuel nitrogen (TFN) decreased as pressure was increased. Also, concentrations of N 2 increased and concentrations of TFN decreased as residence time was increased at 1 atm pressure. For all tests, nitrogen conversion exceeded carbon conversion by about 10%. Neither nitrogen conversion nor carbon conversion was found to increase with increasing pressure. Both increased slightly (4–5%) with increasing residence time, evidence that most of the coal nitrogen and carbon was released during devolatilization.

Effect of pressure on solute diffusivity, solvent viscosity and column temperature in liquid chromatography

The interrelationship between column pressure, solvent viscosity, solute diffusivity and column temperature is complex. Any increase in inlet pressure to provide a higher flow-rate and consequently a faster analysis increases solvent viscosity and column temperature and decreases solute diffusivity. However, a higher column temperature resulting from increased operating pressure reduces the solvent viscosity and increases the solute diffusivity, thereby masking the direct effect of pressure on these variables. Ipso facto, the net effect of pressure and temperature on solute diffusivity for an unthermostated column can be relatively small; consequently, the effect of pressure on column efficiency and column resolution can be minimal for unthermostated columns. However, the effect of this temperature increase on solute retention is very significant for unthermostated columns and leads to a 5% change in the value of k′ for a solute by merely changing the flow-rate from 0.5 to 5 ml/min. Hence, as the heat generated in the column is directly related to the flow-rate and further as the heat transfer through the packed bed of the column is very poor, the use of well thermostated small-bore columns could be mandatory for the precise measurement of solute retention.

Bed to surface heat transfer in a fluidized bed of large particles

Heat transfer coefficients were determined from an immersed cylindrical heater to a fludized bed from the quiescent bed condition to beyond the conditions for maximum bed to surface heat transfer. The experiments were carried out with a range of particles of different thermal and physical properties. Air, argon, carbon dioxide and Freon were used as the fluidizing gases at static pressures up to 1 MN/m 2. Correlations were developed to describe the two components of the overall coefficient: (i) the particle convective component and (ii) the interphase gas convective component. The latter forms an increasing proportion of the overall coefficient as particle size and operating pressure increase.